海上风电交流送出系统谐振过电压产生原因及抑制措施

Causes and Suppression Measures of Resonant Overvoltage in Offshore Wind Power AC Transmission System

电缆单位长度电容为同电压等级架空线路的20倍以上,越来越多的海上风电经交流电缆并网使得送出系统自然谐振频率降低,增大了系统谐振风险。针对某海上风电场并网过程中出现的谐振过电压现象,分析了故障录波数据。基于送出系统阻抗模型进行机理分析,并通过电磁暂态仿真验证了送出系统存在2倍频附近自然谐振频率为风电场合空载变压器、合空载线路操作引发谐振过电压的根本原因。结合工程实际,提出改变送出系统运行方式、优化静止无功发生器控制保护系统和增加接入负荷量的联合抑制措施。最后,通过仿真及现场试验验证了所提措施的有效性。

The capacitance per unit length of a cable is 20 times more than that of an overhead line at the same voltage level,and more and more offshore wind power is connected to the grid through AC cable,which reduces the natural resonant frequency of the transmission system and increases the resonant risk of the system.Aiming at the resonant overvoltage phenomenon in the process of grid connection of an offshore wind farm,the fault recording data are analyzed.Based on the impedance model of the transmission system,the mechanism is analyzed,and through the electromagnetic transient simulation,it is verified that the natural resonant frequency near the double frequency of the transmission system is the fundamental reason for the resonant overvoltage caused by the closing operation of no-load transformer and no-load line in the wind farm.Combined with the engineering practice,the joint suppression measures of changing the operation mode of the transmission system,optimizing the control and protection system of the static var generator and increasing the access load are proposed.Finally,the effectiveness of the proposed measures is verified by simulation and field tests.